simplerefcount.hpp

C++ Templates 完全导引范例

/* The following code example is taken from the book
 * "C++ Templates - The Complete Guide"
 * by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002
 *
 * (C) Copyright David Vandevoorde and Nicolai M. Josuttis 2002.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <stddef.h>  // for the definition of size_t
#include "allocator.hpp"

class SimpleReferenceCount {
  private:
    size_t* counter;    // the allocated counter
  public:
    SimpleReferenceCount () {
        counter = NULL;
    }

    // default copy constructor and copy-assignment operator
    // are fine in that they just copy the shared counter

  public:
    // allocate the counter and initialize its value to one:
    template<typename T> void init (T*) {
        counter = alloc_counter();
        *counter = 1;
    }

    // dispose of the counter:
    template<typename T> void dispose (T*) {
        dealloc_counter(counter);
    }

    // increment by one:
    template<typename T> void increment (T*) {
        ++*counter;
    }
    
    // decrement by one:
    template<typename T> void decrement (T*) {
        --*counter;
    }

    // test for zero:
    template<typename T> bool is_zero (T*) {
        return *counter == 0;
    }
};